A known clutch mechanism related to the field of the invention has been disclosed in Japanese Patent Laid-Open Publication published No. 2001-37155. Especially as described in columns 0066 and 0067 and as illustrated in FIGS. 2 and 9, the clutch mechanism includes an input gear driven for rotation by a driving motor as a driving power source. The clutch mechanism further includes means for operating rotation such as a bushing and a coil. The bushing is engaged with an engaging portion (a second end) of a clutch spring as an operating spring. The coil acts as an electromagnet for attracting a clutch disc to a rotor rotatable together with the input gear by electromagnetic attracting force generated based upon electric current supply. The rotor is engaged with a first end of the clutch spring.
When the electromagnetic attracting force is generated to the coil, the bushing starts rotating together with the rotor and the clutch spring tightens an output hub as a second rotational member. In this case, the output hub is connected to an input hub as a first rotational member integrated with the rotor.
As described, the above-disclosed clutch mechanism includes the coil as the rotation operating means such that the electromagnetic attracting force can be generated by the coil supplied with electric current. In this case, a switching mechanism is required for switching electric current supply to the coil. This may bring a problem of difficulty in downsizing the clutch mechanism and saving weight thereof. Further, this may bring another problem that an actuator installed with the clutch mechanism may be relatively roughly assembled.
A need thus exists for providing an improved clutch mechanism which is more compact and more weight-saved such that the clutch mechanism can be more easily assembled.
Further, in the likely event such as faulty wiring of the driving motor when being assembled, the rotor (the first rotational member) and the busing may rotate in a revere rotational direction relative to a normal rotational direction. In this case, the engaging portion (the second end) of the clutch spring may move relative to the first end thereof in a direction to wind back the clutch spring—i.e., in a direction to expand an inner diameter of the clutch spring, in which the clutch spring may be broken, especially the vicinity of the second end thereof.
A need thus exists for providing an improved clutch mechanism, in which the operating spring may not be easily broken even when the first rotational member rotates in the reverse direction.